Conflicting stories of Mods for the 148 GTL - ST
Richard Camarata
Cobra 148 GTL ST.
They say to cut R131. (Yet I heard from someone that you should not cut the
R131 if you have a radio with Sound Tracker).
Adjust VR10 for the AM power to max it out, (Counter clockwise)
Adjust VR11 for the SSB Power. (Clockwise)
Anybody know what to do with the R131 on a Sound Tracker (ST) Radio?
Thanks.
Handy Andy
Just don't buy an ST when it comes to figuring out what to do with
R131.
Taking R131 out, and having ST, doesn't do anything for it. ST is the
actual "Bottleneck". I'm looking to find sites that actually have
removed the ST function, because I'll link to them due to the sheer
number of questions I'm Emailed about this ST verus non-ST stuff.
While Dancing with the Mouse on Sun, 14 Nov 1999 16:36:32 -0500, the
Modem interrupted with an MNI from ""Richard Camarata"
<rtcam...@mediaone.net>", and the MotherBoard buffered this to Video
RAM:
:+> I have heard conflicting modification procedures for the modulation for the
:+> Cobra 148 GTL ST.
:+>
:+> They say to cut R131. (Yet I heard from someone that you should not cut the
:+> R131 if you have a radio with Sound Tracker).
:+>
:+> Adjust VR10 for the AM power to max it out, (Counter clockwise)
:+> Adjust VR11 for the SSB Power. (Clockwise)
:+>
:+> Anybody know what to do with the R131 on a Sound Tracker (ST) Radio?
:+>
:+> Thanks.
:+>
:+>
Regards!
:+> Andy <+:
. ^ ~- '
. o * . !
... You could be a CB'er when... \\ ^|||^ //
... You spend more time fixing --<< OH DRAT!>>--
... your radio, than talking on it! //|| ||\\
. .-------.
. http://www.iserv.net/~codyspc/ | = oo.~|
. '-------'
cliffhanger
I noticed that your ISP is Iserv. Cool. Im from GR also. Is
handy andy your CB handle? If so, I'll give you a shout sometime.
73's
Cliffhanger
Handy Andy
Yep! And I hang out on Ch 28 mostly in the mornings - about 6:00 to
7:00 during the commute into work.
Have some friends on 2M that I chat with when skip is heavy around
noon. All of them started and still use CB.
While Dancing with the Mouse on Sun, 14 Nov 1999 17:53:51 -0500, the
Modem interrupted with an MNI from "cliffhanger
<spmh...@hotmail.com>", and the MotherBoard buffered this to Video
RAM:
:+> Hi andy,
:+> I noticed that your ISP is Iserv. Cool. Im from GR also. Is
:+> handy andy your CB handle? If so, I'll give you a shout sometime.
:+>
:+> 73's
:+>
:+> Cliffhanger
:+>
Regards!
:+> Andy <+:
..."Gawrsh darn it!"...
Richard Camarata
Handy Andy <Cod...@Iserve.Net> wrote in message
news:382f3210...@news.iserv.net...
> Greetings!
>
> Just don't buy an ST when it comes to figuring out what to do with
> R131.
>
> Taking R131 out, and having ST, doesn't do anything for it. ST is the
> actual "Bottleneck". I'm looking to find sites that actually have
> removed the ST function, because I'll link to them due to the sheer
> number of questions I'm Emailed about this ST verus non-ST stuff.
>
> While Dancing with the Mouse on Sun, 14 Nov 1999 16:36:32 -0500, the
> Modem interrupted with an MNI from ""Richard Camarata"
> <rtcam...@mediaone.net>", and the MotherBoard buffered this to Video
> RAM:
>
> :+> I have heard conflicting modification procedures for the modulation
for the
> :+> Cobra 148 GTL ST.
> :+>
> :+> They say to cut R131. (Yet I heard from someone that you should not
cut the
> :+> R131 if you have a radio with Sound Tracker).
> :+>
> :+> Adjust VR10 for the AM power to max it out, (Counter clockwise)
> :+> Adjust VR11 for the SSB Power. (Clockwise)
> :+>
> :+> Anybody know what to do with the R131 on a Sound Tracker (ST) Radio?
> :+>
> :+> Thanks.
> :+>
> :+>
>
>
> Regards!
> :+> Andy <+:
> . ^ ~- '
> . o * . !
> ... You could be a CB'er when... \\ ^|||^ //
> ... You spend more time fixing --<< OH DRAT!>>--
> ... your radio, than talking on it! file://|| ||\\
Jack Thurston
Does the R131 affect the SSB Power???
No, it doesn't!
Jack
Handy Andy
No, TR34 ALC sense/amp connects to TR25 AMC/ALC amp.
R131 affects TR26 AMC sense/amp.
<Why? This is where it gets long winded. Readers are invited to
comment...>
The bad thing about TR26, is the inherent fault of placing the emitter
on the AM regulator output line to the finals, audio is always applied
to the emitter versus using the base and running it as a limiter
versus a regulator in itself when the radios' in AM mode.
It conducts when the base voltage reference done by R131 and R130
affects the emitter voltage off the sense line from AM regualtor. It
begins to begins to fall when audio is applied. Falls too far, the
emitter of TR26 is at a lower reference voltage than the base, and
begins to conduct, pulling TR25s' base low and this forces TR25 to
work. By sensing the dropping DC voltage, this circuit operates to
prevent negative peaks from forcing cuttoff at the Finals. The forward
swing is allowed, but C109 acts as a peak/hold filter that recovers
thru a series of set limiter resistors.
It's a cascade effect. Under SSB mode, this automatically biases off
TR26 [straight 12V reverse biases the emitter but the collector
acheives a high impedance 8 volts to provide a reference to TR25 due
to what R131 and R130, along with R129/R128 provide to the sense
line].
In SSB, TR34 runs TR25 instead. TR25 conducts when it's base voltage
is pulled below the reference voltage R129/R128 gives from the line
shared by the collectors of TR26 and TR34.
Due to the biasing of the base of TR26, the collector output is a
steady voltage, but at a high-impedance set by R130 and R131 and
TR25's R128/R129.
A small change in voltage on TR34's collector affects the collector of
TR26 and the base of TR25, and TR25 acts like a switch and changes
it's state [due to the bias reference of R129/R128] and a capacitor
10uF acts like a filter and also something to work against when the
charge removed from C109 is recovered due to biasing
R128/R129/R130/R131 provide. That in turn forces the AF limiter TR24
to conduct.
In AM mode, 8 volts constant is applied to the emitter of TR34, so any
sensing of envelope exceeding a refrence TR34 wants to conduct on, it
can't, no current flows because the emitter is reverse biased.
Whats a pain, is you'd think that simply removing TR26 would take care
of the problem right? Alas, it's not that way. A voltage needs to be
present to make TR25 remain off, and because of the 8 volt constant
used to regulate the base of TR26, this is where the ALC works against
a set value, and TR25 remains off until TR24 pulls this reference
voltage low enough to force TR24 to conduct and limit audio. R128
offers high-impedance to TR34, but will always have a voltage present
on it due to the forward voltage drop of TR26's collector to base and
R130. So, it will always provide a voltage sense and is why TR26 needs
to remain there. The collector to base drop is only .7 volts, but
R130, along with R128/R129, gives TR34's sense line some reference,
only at a high impedance, and a slight change of this line and TR25
acts like it did before. R128 drains off R129's reference from 8 volts
constant.
[condensed from my notes over a Cobra 148 - due to labeling and
additional changes, some parts noted above may vary from 148 to 148 ST
models.]
There's ways around this of course, but TR24 being removed or R131, is
the down and dirty way, except removing TR24 is inherently affecting
both modes and is a lot dirtier in results.
Removing R131 takes care of the 8 volt reference TR26 needs, it then
remains conducting due to R130 keeping the base reference to ground,
but keeping the emitter effectively "off" all the time - no matter
what voltage may be present at the emitter. The radio is not capable
of dropping that much in AM regulation voltage on the emitter to go
below base reference R130 has.
But, due to the bleedoff of R129 from the base of TR25 and R128 and
forward voltage drop and bias of collector to base of TR26 and R130,
this reference voltage is close to, but not quite at the same voltage
had R131 been in place.
Hopefully I have this right...;-)
While Dancing with the Mouse on Sun, 14 Nov 1999 19:24:04 -0500, the
Modem interrupted with an MNI from ""Richard Camarata"
<rtcam...@mediaone.net>", and the MotherBoard buffered this to Video
RAM:
:+> Does the R131 affect the SSB Power???
Regards!
:+> Andy <+:
. ^ ~- '
. o * . !
... You could be a CB'er when... \\ ^|||^ //
... You spend more time fixing --<< OH DRAT!>>--
... your radio, than talking on it! //|| ||\\
Tim
Good luck and best regards from Tim 082.
IR-DX Group http://home.wxs.nl/~19ir01
LD-DX Group http://come.to/limadelta
Kp-DX Group http://www.gate.net/~kp
Daily Updated 11 Meter DX News
http://home.t-online.de/home/IRDX.GERMany/dxnews~1.htm
SCSI UDMA
MC Turner
helps him! Leave the carrier adjustment alone and turn the AMC up or cut R131
and put the cover back on..
MC
Richard Camarata wrote:
> I have heard conflicting modification procedures for the modulation for the
> Cobra 148 GTL ST.
>
> They say to cut R131. (Yet I heard from someone that you should not cut the
> R131 if you have a radio with Sound Tracker).
>
> Adjust VR10 for the AM power to max it out, (Counter clockwise)
> Adjust VR11 for the SSB Power. (Clockwise)
>
> Anybody know what to do with the R131 on a Sound Tracker (ST) Radio?
>
> Thanks.
Hank Aaron
the Cobra 148 GTL.
Remove C35 and C16. Short pins 3-(red wire) and 5 (yellow wire) of the
connector on the channel selector PCB.
I have found by study that this is the most direct way (while best sounding)
of smashing ST more less.
Hank
Handy Andy wrote in message <382f3210...@news.iserv.net>...
>Greetings!
>
>Just don't buy an ST when it comes to figuring out what to do with
>R131.
>
>Taking R131 out, and having ST, doesn't do anything for it. ST is the
>actual "Bottleneck". I'm looking to find sites that actually have
>removed the ST function, because I'll link to them due to the sheer
>number of questions I'm Emailed about this ST verus non-ST stuff.
>
>While Dancing with the Mouse on Sun, 14 Nov 1999 16:36:32 -0500, the
>Modem interrupted with an MNI from ""Richard Camarata"
><rtcam...@mediaone.net>", and the MotherBoard buffered this to Video
>RAM:
>
>:+> I have heard conflicting modification procedures for the modulation for
the
>:+> Cobra 148 GTL ST.
>:+>
>:+> They say to cut R131. (Yet I heard from someone that you should not
cut the
>:+> R131 if you have a radio with Sound Tracker).
>:+>
>:+> Adjust VR10 for the AM power to max it out, (Counter clockwise)
>:+> Adjust VR11 for the SSB Power. (Clockwise)
>:+>
>:+> Anybody know what to do with the R131 on a Sound Tracker (ST) Radio?
>:+>
>:+> Thanks.
>:+>
>:+>
>
>
>Regards!
>:+> Andy <+:
>. ^ ~- '
>. o * . !
>... You could be a CB'er when... \\ ^|||^ //
>... You spend more time fixing --<< OH DRAT!>>--
>... your radio, than talking on it! file://|| ||\\
Toadster
better modulation and slightly higher AM carrier wattage. Cutting R131
makes the radio over sensitive
Hank Aaron <REMOVEjef...@hotmail.com> wrote in message
news:80qid2$be1$1...@nntp6.atl.mindspring.net...
Buckaroo223
way you turn it. RV10 for AM power.
Buckaroo "223"
Richard Camarata
I'll try to compile all the info and come up with a step-by-step process for
the Mods.
Sounds as if this beast of a radio is one of the most difficult to properly
modify.
Good think I waited for the input of this group.
I would conclude that the ST must be taken care of prior to mods.
Too bad it was useful to pull in weak AM. (Horrible for SSB).
I'll wait a few more days until the posts stop, then make the mods.
Sure do wish I could pass the game plan by someone prior to committing.
Handy Andy <Cod...@Iserve.Net> wrote in message
news:3831f2eb...@news.iserv.net...
> Greetings!
>
> Thank you. I thought there was few more parts, but you are correct.
>
> My memory needs post-it note pads!
>
> Too bad I fixed and gave it back, it's the one I had the headaches
> over. I remember them asking to have it defeated and do some work.
> After jumpering the ST switch I set about working on it, I know
> theres' some other stuff that these two caps address, but the radio is
> back in their hands. And they like the work. So, I'm sure someone else
> will get their fingers in it and post some more mods out here soon.
>
> I just wish I remembered more of that had to be done. I do remember it
> took the mods rather well. Mostly modulation and some re-work of the
> driver/final section, and it was up to snuff and good enough!
>
> 4 months and a Divroce does that to people...sigh...
>
> While Dancing with the Mouse on Mon, 15 Nov 1999 19:28:15 -0500, the
> Modem interrupted with an MNI from ""Hank Aaron"
> <REMOVEjef...@hotmail.com>", and the MotherBoard buffered this
> to Video RAM:
>
> :+> These steps should be absolutely taken before using "common" found
mods for
> :+> the Cobra 148 GTL.
> :+>
> :+> Remove C35 and C16. Short pins 3-(red wire) and 5 (yellow wire) of
the
> :+> connector on the channel selector PCB.
> :+>
> :+> I have found by study that this is the most direct way (while best
sounding)
> :+> of smashing ST more less.
> :+>
> :+> Hank
> :+>
> :+>
> :+>
> :+> Handy Andy wrote in message <382f3210...@news.iserv.net>...
> :+> >Greetings!
> :+> >
> :+> >Just don't buy an ST when it comes to figuring out what to do with
> :+> >R131.
> :+> >
> :+> >Taking R131 out, and having ST, doesn't do anything for it. ST is the
> :+> >actual "Bottleneck". I'm looking to find sites that actually have
> :+> >removed the ST function, because I'll link to them due to the sheer
> :+> >number of questions I'm Emailed about this ST verus non-ST stuff.
> :+> >
> :+> >While Dancing with the Mouse on Sun, 14 Nov 1999 16:36:32 -0500, the
> :+> >Modem interrupted with an MNI from ""Richard Camarata"
> :+> ><rtcam...@mediaone.net>", and the MotherBoard buffered this to
Video
> :+> >RAM:
> :+> >
> :+> >:+> I have heard conflicting modification procedures for the
modulation for
> :+> the
> :+> >:+> Cobra 148 GTL ST.
> :+> >:+>
> :+> >:+> They say to cut R131. (Yet I heard from someone that you should
not
> :+> cut the
> :+> >:+> R131 if you have a radio with Sound Tracker).
> :+> >:+>
> :+> >:+> Adjust VR10 for the AM power to max it out, (Counter clockwise)
> :+> >:+> Adjust VR11 for the SSB Power. (Clockwise)
> :+> >:+>
> :+> >:+> Anybody know what to do with the R131 on a Sound Tracker (ST)
Radio?
> :+> >:+>
> :+> >:+> Thanks.
> :+> >:+>
> :+> >:+>
> :+> >
> :+> >
> :+> >Regards!
> :+> >:+> Andy <+:
> :+> >. ^ ~- '
> :+> >. o * . !
> :+> >... You could be a CB'er when... \\ ^|||^ //
> :+> >... You spend more time fixing --<< OH DRAT!>>--
> :+> >... your radio, than talking on it! file://|| ||\\
> :+> >. .-------.
> :+> >. http://www.iserv.net/~codyspc/ | = oo.~|
> :+> >. '-------'
> :+>
> :+>
>
> Regards!
> :+> Andy <+:
>
> ... You know you're no longer a mud-duck when...
> ... You break their squelch, owe them a new needle,
> ... and rattle their speakers so bad that their
> ... Dentures fall out!
> . --- Handy Andy
>
> http://www.iserv.net/~codyspc
Hank Aaron
genius (I pretend I am to myself though) I thought this information was old
news. I apologize for not contributing earlier:
25WST
Remove C809 and C819. Short pins 1 & 2 of IC802.
29WST
Remove C821 and C809. Short pins 1 & 2 of IC802.
29LTD-NH
Remove C809. Cut trace between IC801 pin 10, and IC802 pin 4. Short pins 1
& 2 of IC802.
148GTL-ST
Remove C35 and C16. Short pins 3 & 5 of the connector on the channel
selector PCB.
I believe I go them in order. I'll help where I can, just email me.
Hank
Richard Camarata wrote in message ...
)====}lllllllllllllllll}>------
Buckaroo223 <cb...@aol.com> wrote in message
news:19991116173749...@ng-fq1.aol.com...
Handy Andy
Handy Andy
It was just a bear. Once you we're able to make it work straight
forward, it performed like all the other radios.
The thing I liked about ST, which led me into this mess with the radio
I got to work on, was it's novel use of a compandor. To dis-able the
ST, I just jumpered at first, then payed attention to what it was
doing.
...what seemed like hundereds of hours later and constant references
to electronic references in "Audio sections"...
... I finally came to a concussion, er-conclusion, that ST for what it
is, needs to be made "Globally" implemented for it to really work like
it should for others to hear the benefit. Too bad the FCC didn't allow
for a PL to be broadcast so that these ST radios could have the full
benefit of detecting the PL and engaging during such a transmission
from another ST radio to hear the true benefit.
I actually had two ST-models, one a Cobra 29, and one the 148.
The 29 I simply re-overhauled, fixed the ST and sold it at a local
Flea market.
I actually lost money on it. It cost me 5 bucks at a Garage sale, but
after all the work I put into the '29, I only got 30 bucks. This
radio was the one I originally got, and had to re-connect the ST
feature to make it work. [Or at least undo what they did, and
re-create the original and then fix that.]
Once I got the '29 working, the 148 came into play. It still has the
ST circuits intact, only bypassed. They use the ST button for a
channel jump switch.
But, to give credit, the joy of ST was the "expansion" after it got
into the other receivers' ST. Very good fidelity, but sounded a lot
"flatter" on another radio that didn't have ST.
This is the reason why ST is such a bane. It sounds great when two
radios use it, but terrible on other radios not equipped for decoding
it.
As far as mods? Well, be conservative at first. Don't go all out for
doing it all at once. Take your time and use the radio in-between mods
This way, if someone complains, you only need to re-do one mod, and
not have to re-fix everything else.
Believe me, I've been there.
While Dancing with the Mouse on Tue, 16 Nov 1999 20:06:03 -0500, the
Modem interrupted with an MNI from ""Richard Camarata"
<rtcam...@mediaone.net>", and the MotherBoard buffered this to Video
RAM:
:+> Good Info... Thanks.
:+>
:+> I'll try to compile all the info and come up with a step-by-step process for
:+> the Mods.
:+>
:+> Sounds as if this beast of a radio is one of the most difficult to properly
:+> modify.
:+> Good think I waited for the input of this group.
:+>
:+> I would conclude that the ST must be taken care of prior to mods.
:+> Too bad it was useful to pull in weak AM. (Horrible for SSB).
:+>
:+> I'll wait a few more days until the posts stop, then make the mods.
:+>
:+> Sure do wish I could pass the game plan by someone prior to committing.
:+>
:+>
:+> Handy Andy <Cod...@Iserve.Net> wrote in message
:+> news:3831f2eb...@news.iserv.net...
:+> > Greetings!
:+> >
:+> > Thank you. I thought there was few more parts, but you are correct.
:+> >
:+> > My memory needs post-it note pads!
:+> >
:+> > Too bad I fixed and gave it back, it's the one I had the headaches
:+> > over. I remember them asking to have it defeated and do some work.
:+> > After jumpering the ST switch I set about working on it, I know
:+> > theres' some other stuff that these two caps address, but the radio is
:+> > back in their hands. And they like the work. So, I'm sure someone else
:+> > will get their fingers in it and post some more mods out here soon.
:+> >
:+> > I just wish I remembered more of that had to be done. I do remember it
:+> > took the mods rather well. Mostly modulation and some re-work of the
:+> > driver/final section, and it was up to snuff and good enough!
:+> >
:+> > 4 months and a Divroce does that to people...sigh...
:+> >
:+> > While Dancing with the Mouse on Mon, 15 Nov 1999 19:28:15 -0500, the
:+> > Modem interrupted with an MNI from ""Hank Aaron"
:+> > <REMOVEjef...@hotmail.com>", and the MotherBoard buffered this
:+> > to Video RAM:
:+> >
:+> > :+> These steps should be absolutely taken before using "common" found
:+> mods for
:+> > :+> the Cobra 148 GTL.
:+> > :+>
:+> > :+> Remove C35 and C16. Short pins 3-(red wire) and 5 (yellow wire) of
:+> the
:+> > :+> connector on the channel selector PCB.
:+> > :+>
:+> > :+> I have found by study that this is the most direct way (while best
:+> sounding)
:+> > :+> of smashing ST more less.
:+> > :+>
:+> > :+> Hank
:+> > :+>
:+> > :+>
:+> > :+>
:+> > :+> Handy Andy wrote in message <382f3210...@news.iserv.net>...
:+> > :+> >Greetings!
:+> > :+> >
:+> > :+> >Just don't buy an ST when it comes to figuring out what to do with
:+> > :+> >R131.
:+> > :+> >
:+> > :+> >Taking R131 out, and having ST, doesn't do anything for it. ST is the
:+> > :+> >actual "Bottleneck". I'm looking to find sites that actually have
:+> > :+> >removed the ST function, because I'll link to them due to the sheer
:+> > :+> >number of questions I'm Emailed about this ST verus non-ST stuff.
:+> > :+> >
:+> > :+> >While Dancing with the Mouse on Sun, 14 Nov 1999 16:36:32 -0500, the
:+> > :+> >Modem interrupted with an MNI from ""Richard Camarata"
:+> > :+> ><rtcam...@mediaone.net>", and the MotherBoard buffered this to
:+> Video
:+> > :+> >RAM:
:+> > :+> >
:+> > :+> >:+> I have heard conflicting modification procedures for the
:+> modulation for
:+> > :+> the
:+> > :+> >:+> Cobra 148 GTL ST.
:+> > :+> >:+>
:+> > :+> >:+> They say to cut R131. (Yet I heard from someone that you should
:+> not
:+> > :+> cut the
:+> > :+> >:+> R131 if you have a radio with Sound Tracker).
:+> > :+> >:+>
:+> > :+> >:+> Adjust VR10 for the AM power to max it out, (Counter clockwise)
:+> > :+> >:+> Adjust VR11 for the SSB Power. (Clockwise)
:+> > :+> >:+>
:+> > :+> >:+> Anybody know what to do with the R131 on a Sound Tracker (ST)
:+> Radio?
:+> > :+> >:+>
:+> > :+> >:+> Thanks.
:+> > :+> >:+>
:+> > :+> >:+>
:+> > :+> >
:+> > :+> >
:+> > :+> >Regards!
:+> > :+> >:+> Andy <+:
:+> > :+> >. ^ ~- '
:+> > :+> >. o * . !
:+> > :+> >... You could be a CB'er when... \\ ^|||^ //
:+> > :+> >... You spend more time fixing --<< OH DRAT!>>--
:+> > :+> >... your radio, than talking on it! file://|| ||\\
:+> > :+> >. .-------.
:+> > :+> >. http://www.iserv.net/~codyspc/ | = oo.~|
:+> > :+> >. '-------'
:+> > :+>
:+> > :+>
:+> >
:+> > Regards!
:+> > :+> Andy <+:
:+> >
:+> > ... You know you're no longer a mud-duck when...
:+> > ... You break their squelch, owe them a new needle,
:+> > ... and rattle their speakers so bad that their
:+> > ... Dentures fall out!
:+> > . --- Handy Andy
:+> >
:+> > http://www.iserv.net/~codyspc
:+>
:+>
Regards!
:+> Andy <+:
.
. |!?! |
. ZAP! _| __/
... You know your LINEAR is working when... _| __/
... Fashion jewelry, being worn by people \ _/
... around you, starts arcing! \/
. OUCH
. http://www.iserv.net/~codyspc/CBRADIO.HTM
Jack Thurston
R131 still disables amc in the 148 gtl-st.
Remove C132 to regain full ssb power range
across the travel of the ssb alc control.
Jack
P.S. If you pulled a resistor out thinking
it is R131 but no increase in am modulation,
you pulled the wrong one!